Michelangelo Merisi da Caravaggio (1571-1610) lived the darkest and most dangerous life of any of the great painters. So says the jacket blurb of the latest attempt on that life, by Andrew Graham-Dixon, whose biography of the painter is subtitled, lip-smackingly, "a life sacred and profane". As with Van Gogh, only more so, there is much lip-smacking about Caravaggio. Murder and pederasty trump mutilation and madness, and - alone among the great artists? - Caravaggio killed a man (a pimp, to boot). As for the pederasty, it may be that prurient interest has got the better of proper scepticism; or it may not. At the very least, it is clear beyond peradventure that Caravaggio lived his life with an alarming lack of restraint.

The documentation on an artist of this period is bound to be patchy, gossipy and contradictory, as Giorgio Vasari's Lives of the Artists goes to show. Regrettably, Caravaggio was born just after Vasari completed his labours, but the documentation on him is uncommonly rich precisely because he was so often collared by the law. Apart from anything else, he was easily provoked.

On one occasion, in the Osteria del Moro in Rome, he asked the waiter whether the artichokes were done in butter or in oil. The waiter responded with a certain waiterly superiority that he did not know, picked one up and put it to his nose. Caravaggio took this as an insult, or a slight. The Romans prided themselves on their olive oil; the town from which Caravaggio took his name was in Lombardy, up north - for the discriminating Roman, he was a hick from the sticks. Such was the painter's interpretation of the waiter's gesture. He seized the plate and threw it at the waiter's face, with a choice insult of his own, "becco fottuto" ("fucked-over cuckold"). Given the length of the charge-sheet, lack of restraint in language is perhaps a peccadillo, but it is somehow indicative of the man, and the life. Caravaggio had temperament, as Cézanne would have said.

One of the most remarkable features of Michael Fried's remarkable study of him is that he is hardly interested in Caravaggio's personality or biography. The Moment of Caravaggio is not so much a life and times as a work and times, a forensic investigation, not of the crimes, but of the paintings. In the circumstances, it might well be thought that this is something of a handicap, a little like a study of Van Gogh without the mental turmoil, or Picasso without the women, or Proust without the cork-lined room, or Trotsky without the ice pick.

And indeed, there are aspects of the work that appear to invite a biographical treatment. If Fried is right - and he is very persuasive - Caravaggio was centrally concerned with the kind of painting that demanded and received prolonged attention; he must have been encouraged in that ambition by his patrons, who commissioned the work, and fed and watered and sheltered the artist, for these were the people with the time and the taste for such long looking. They were also the people with the private galleries, which were perhaps the only places where prolonged, uninterrupted viewing was a practical proposition.

On this analysis, therefore, they constituted a sort of Caravaggio community, or extended family, of like-minded persons (patrons) who prized the paintings for exactly the qualities that mattered most to Caravaggio himself, and who nurtured both the art and the artist. That in turn has biographical implications, as Fried notes, in a rare throwaway remark about "the persistence of the myth of Caravaggio-as-outlaw". On the family model, he was more in-law than outlaw. However that may be, the argument cannot be settled without a more sustained engagement with the life.

What was Caravaggio after, according to Fried? Put differently, why do these paintings speak to us so? Fried's wrestling with this intractable question is what gives his own work its intensive stamp and its propulsive thrust. He fastens on what he calls the absorptive or immersive quality of Caravaggio's art, its "intensely imagined inwardness", which has the power to hold us and keep us, rapt in contemplation; we enter into the painting, with no thought of escape. We are drawn to the people in the paintings rather as we are drawn to people in life. Even the minor characters make a greater impression on us than some of our personal relationships. We are absorbed in them, just as they are absorbed in whatever it is they are doing, or observing. Extraordinarily, we enter their world. "Thus art 'outdoes' life, precisely by foregrounding its character as art."

This is Fried in high gear, and the ride is thrilling and demanding at the same time. He is not only a great scholar but also a great reasoner, the heavyweight champion of his field, his combination of dialogical springiness and brainy muscularity rivalled only by his contemporary T. J. Clark. (He is also a poet. New readers might venture The Next Bend in the Road.) Fried has no time for the Proustian proposition that "a work in which there are theories is like an object with its price tag still attached". He revels in theories, or at any rate in arguments, and The Moment of Caravaggio is chock-full of them. The noteworthy thing is that they are mostly his own.

Readers familiar with his earlier work will recognise the preoccupation with absorption from an influential thesis on "absorption" versus "theatricality" in the art of Courbet and Manet. This distinction resurfaces here, in adapted form. Not only is Caravaggio outed as the inventor of absorption, but Fried also identifies two "moments" in the production of his paintings: the "immersive" moment and the "specular" moment. The "immersive" moment is not really a moment at all, but a period of extended duration when the painter is engaged in the act of painting - Fried offers a brilliant new reading of several paintings as disguised mirror representations of the act of painting. The "specular" moment is when the painter detaches himself from the painting, establishing the painted image as an image, and the painting as a picture addressed to a viewer. Caravaggio's fondness for beheadings, including a self-portrait of his own severed head in the wondrous David with the Head of Goliath, is the ultimate in detachment, and yet also the picture of absorption - a truly Friedian moment.

Lest all this seem a little too immersive for comfort, the life, or rather the afterlife, offers a striking correlative. Caravaggio has a strong appeal for film-makers. The devotees include Martin Scorsese, whose Mean Streets and Taxi Driver made use of him for set design and camera angles. Spookily enough, Scorsese sounds just like Michael Fried: "Initially I related to the paintings because of the moment that he chose to illuminate in the story. The Conversion of Paul, Judith Beheading Holofernes: he was choosing a moment that was not the absolute moment of the beginning of the action, it's during the action, in a way. You sort of come upon the scene midway and you're immersed in it."

Travis Bickle, David and Goliath, they are all the same. "Are you talking to me? You must be, 'cause I'm the only one here."

THE AUTHOR

Michael Fried is the J.R. Herbert Boone professor of humanities and art history at Johns Hopkins University. The renowned art critic and art historian majored in English. It was during undergraduate studies at Princeton University that he became interested in art criticism and followed this up with studies at the University of Oxford's Ruskin School of Drawing and Fine Art. After studying philosophy part time at University College London, Fried undertook doctoral studies in art history at Harvard University.

He has said that if he were marooned on a desert island, he would take with him a book of Heinrich von Kleist's stories - but he would "petition to be allowed to also take with him the same author's play The Prince of Hamburg".

He does not consider academic writing the most difficult pastime: "There is nothing harder to do than to write a successful poem."